System and method for retransmitting packets over a network of communication channels

ABSTRACT

System and methods for transmitting packets over a network are provided. A system includes a network access coordinator (NAC) configured to communicate with first and second nodes via a network backbone. The NAC is configured to coordinate access of the first and second nodes to the network backbone. The NAC is configured to receive, from the first node in a first time period, a first reservation request to transmit a first packet to the second node. The NAC is configured to allocate, in response to the first reservation request, a first slot in a second time period for the first node to transmit the first packet to the second node. The NAC is configured to allocate a second slot for the second node to transmit, to the first node, a first reply that includes an indicator of whether the second node received the first packet.

REFERENCE TO CO-PENDING APPLICATIONS

This application claims priority as a continuation application from U.S.patent application Ser. No. 12/731,291, filed on Mar. 25, 2010, whichclaims priority as a continuation application from U.S. patentapplication Ser. No. 11/942,114, filed on Nov. 19, 2007, issued as U.S.Pat. No. 7,742,495, which is a nonprovisional of the following U.S.Provisional Applications: U.S. Provisional Application No. 60/866,532,entitled, “A METHOD FOR PACKET AGGREGATION IN A COORDINATED HOMENETWORK,” filed on Nov. 20, 2006; U.S. Provisional Application No.60/866,527, entitled, “RETRANSMISSION IN COORDINATED HOME NETWORK,”filed on Nov. 20, 2006; U.S. Provisional Application No. 60/866,519,entitled, “IQ IMBALANCE CORRECTION USING 2-TONE SIGNAL IN MULTI-CARRIERRECEIVERS,” filed on Nov. 20, 2006; U.S. Provisional Application No.60/907,111, entitled, “SYSTEM AND METHOD FOR AGGREGATION OF PACKETS FORTRANSMISSION THROUGH A COMMUNICATIONS NETWORK,” filed on Mar. 21, 2007;U.S. Provisional Application No. 60/907,126, entitled, “MAC TO PHYINTERFACE APPARATUS AND METHODS FOR TRANSMISSION OF PACKETS THROUGH ACOMMUNICATIONS NETWORK,” filed on Mar. 22, 2007; U.S. ProvisionalApplication No. 60/907,819, entitled, “SYSTEMS AND METHODS FORRETRANSMITTING PACKETS OVER A NETWORK OF COMMUNICATION CHANNELS,” filedon Apr. 18, 2007; and U.S. Provisional Application No. 60/940,998,entitled “MOCA AGGREGATION,” filed on May 31, 2007. All of the foregoingapplications are hereby incorporated by reference in their entirety forall purposes.

FIELD OF THE INVENTION

The present invention relates generally to information networks andspecifically to transmitting information such as media information overcommunication lines such as coaxial conductor cables (hereinafter,“coax”).

BACKGROUND OF THE INVENTION

Home networking over coax is a known technology which has vastcommercial potential.

The Multimedia over Coax Alliance (“MoCA™”), at its websitemocalliance.org, provides an example of a suitable specification (MoCA1.0) for transmitting digital video and entertainment informationthrough coaxial cable deployed in a building, home or other structure orregion. The specification has been distributed to an open membership.

MoCA 1.0 is but one example of a suitable home networking technology.MoCA and similar technologies tap into the unused bandwidth available ondeployed coax. More than 70% of homes in the United States have deployedcoax. Many have coax in one or more primary entertainment locations,such as family rooms, media rooms and master bedrooms. MoCA or othersuitable technologies allow homeowners to utilize the coax as anetworking system and to deliver other entertainment and informationprogramming with high quality of service (“QoS”).

The technology underlying MoCA, for example, provides high speed (270mbps), high QoS, and the innate security of a shielded, wired connectioncombined with state-of-the-art packet-level encryption. Coax is designedfor carrying high bandwidth video. Today, it is regularly used tosecurely deliver millions of dollars of pay-per-view and premium videocontent on a daily basis. The MoCA network, or other similar suitablenetworks, can also be used as a backbone for multiple wireless accesspoints used to extend the reach of wireless communication throughout ahome.

MoCA, or other similar suitable technologies, can typically provide aconsistent, high throughput, high quality connection through deployedcoaxial cables to video devices in the home without affecting the analogor digital services present on the cable. MoCA provides a primary linkfor digital entertainment, and may also act in concert with other wiredand wireless networks to extend entertainment throughout the home.

MoCA works with access technologies such as ADSL and VDSL services orFiber to the Home (FTTH), that typically enter the home on a twistedpair or on an optical fiber, operating in a frequency band from a fewhundred kilohertz to 8.5 MHz for ADSL and 12 MHZ for VDSL. As servicesreach the home on via xDSL or FTTH, they may be routed via MoCAtechnology and the in-home coax to the video devices. Cablefunctionalities, such as video, voice and Internet access, may beprovided to homes, via coaxial cable, by cable operators, and usecoaxial cables running within the homes to reach individual cableservice consuming devices locating in various rooms within the home.Typically, MoCA type functionalities run in parallel with the cablefunctionalities, on different frequencies.

Coax infrastructure inside a house typically includes coaxial wires andsplitters. Splitters used in homes typically have one input and two ormore outputs and are designed to transfer signals from input to outputsin the forward direction, or from outputs to input in the backwarddirection and to isolate splitter outputs and prevent signals fromflowing room/outlet to room/outlet. Isolation is useful in order to a)reduce interference from other devices and b) maximize power transferfrom Point Of Entry (POE) to outlets for best TV reception.

The MoCA technology is specifically designed to go backwards throughsplitters (insertion) and go from splitter output to output (isolation).All outlets in a house can be reached from each other by a single“isolation jump” and a number of “insertion jumps”. Typically, isolationjumps have an attenuation of 5 to 40 dB and each insertion jumpattenuates approximately 3 dB. MoCA has a dynamic range in excess of 55dB while supporting 200 Mbps throughput. Therefore MoCA can workeffectively through a significant number of splitters.

MoCA is a managed network unlike some other home networkingtechnologies. It is specifically designed to support streaming videowithout packet loss providing very high video quality between outlets.

Digital cable programming is delivered with threshold Packet Error Rate(PER) of below 1e-6. The home network may preferably have similar orbetter performance so as not to degrade viewing.

The disclosures of any publications and patent documents mentioned inthe specification, and of the publications and patent documents citedtherein directly or indirectly, are hereby incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention, its nature andvarious advantages will be more apparent upon consideration of thefollowing detailed description, taken in conjunction with theaccompanying drawings, and in which:

FIG. 1 is a prior art timing diagram;

FIG. 2 is an illustrative timing diagram in accordance with theprinciples of the invention;

FIG. 3 is another illustrative timing diagram in accordance with theprinciples of the invention;

FIG. 4 is yet another illustrative timing diagram in accordance with theprinciples of the invention;

FIG. 5 is still another illustrative timing diagram in accordance withthe principles of the invention;

FIG. 6 is another illustrative timing diagram in accordance with theprinciples of the invention;

FIG. 7 is an illustrative timing diagram in accordance with theprinciples of the invention;

FIG. 8 is another illustrative timing diagram in accordance with theprinciples of the invention; and

FIG. 9 is an illustrative timing diagram in accordance with theprinciples of the invention.

FIG. 10 shows schematically an illustrative device that may be used inaccordance with the principles of the invention.

FIG. 11 shows an illustrative home network system in accordance with theprinciples of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides improved systems and methods forstreaming media over coax.

Some embodiments of the invention may include a system for transmittingpackets over a network of communication channels. The system may includea set of nodes comprising at least first and second nodes and a networkaccess coordinator operative to coordinate the access of the set ofnodes to a synchronous network of channels, wherein, if at least oneindividual packet has been transmitted from the first node to the secondnode which did not receive at least one packet, the second node isoperative to send a retransmission request to the network accesscoordinator requesting retransmission of at least one individual packet.

The network may have a Coordinated MAC to allow contention free access.The coordinated MAC may be a home network coordinated MAC such as, forexample, that described in the MoCA MAC/PHY SPECIFICATION v. 1.0 (“theMoCA Specification”), Feb. 22, 2006, which is hereby incorporated hereinin its entirety. The MoCA Specification identifies features of a homenetwork over existing coaxial cable. The method may allow the expansionof the coordinated network MAC to other media in the home like powerlines and phone lines (or wireless) to improve the accessibility of thenetwork to rooms in the home that are not accessible via coaxial cables.

The retransmission request for an individual packet which failed totransmit in MAP cycle N may occur in MAP cycle N+1.

The network access coordinator may be operative to receive and to accedeto the retransmission request.

The retransmission of an individual packet which failed to transmit inMAP cycle N may occur in MAP cycle N+2.

Some embodiments of the invention may include a system for transmittingpackets over a network of communication channels. The system may includea set of nodes interconnected by a synchronous network of channels and anetwork access coordinator operative to coordinate the access of the setof nodes to the synchronous network of channels including providing aplurality of slots in each MAP cycle for packet transmission requestssent to the coordinator by individual nodes in the set of nodes, andwherein at least one individual node in the set of nodes is operative toutilize an individual slot from among the plurality of slots to transmitto the coordinator both a reservation request and a retransmissionrequest, the reservation request including a request to transmit a firstpacket to a first additional node and the retransmission requestincluding a request that a second additional node retransmit a secondpacket previously unsuccessfully transmitted from the second additionalnode to the individual node.

In some embodiments, the network access coordinator may be operative toprovide a plurality of slots in each MAP cycle for packet transmissionrequests sent to the coordinator by individual nodes in the set ofnodes. At least one individual node in the set of nodes may be operativeto utilize an individual slot from among the plurality of slots totransmit to the coordinator both a reservation request and aretransmission request, the reservation request including a request totransmit a first packet to a first additional node and theretransmission request including a request that a second additional noderetransmit a second packet previously unsuccessfully transmitted fromthe second additional node to the individual node.

In some embodiments, if a plurality of packets have been transmittedfrom the first node to the second node which did not receive at leastsome of the plurality of packets, the second node may be operative tosend a single burst to the network access coordinator. The burst mayinclude retransmission requests requesting retransmission of thosepackets from among the plurality of packets which were not received.

In some embodiments, a retransmission request sent by the second node ina MAP cycle N may requests retransmission of only those packets whichwere not received by the second node in a previous MAP cycle N−1.

In some embodiments, overhead information which is common to thereservation request and the re-transmission request may be transmittedby the individual node to the coordinator only once.

In some embodiments, if the first node sent the second node, in a MAPcycle N1, an aggregation frame including a plurality of packets onlysome of which were received by the second node, in MAP cycle N, thesecond node may refrain from requesting retransmission of those packets,from among those sent in MAP cycle N−1, which were successfully receivedand successfully de-aggregated by the second node.

In some embodiments, at least one retransmission request may include anindication of a slot duration to be used to retransmit the individualpacket.

In some embodiments, if the first node sent the second node , in a MAPcycle N−1, an aggregation frame including a plurality of packets onlysome of which were received by the second node, the retransmissionrequest sent by the second node to the network access coordinator mayrequest retransmission of less than all of the plurality of packets andmay include an indication, computed by the second node, of a slotduration to be used to retransmit the packets for which retransmissionis requested.

In some embodiments, a retransmission request sent by the individualnode in a MAP cycle N requests retransmission of only those packetswhich were not received by the individual node in a previous MAP cycleN−1.

In some embodiments, if in a MAP cycle N−1, the second additional nodesent the individual node an aggregation frame including a plurality ofpackets, only some of which were received by the individual node, in MAPcycle N, the individual node may refrain from requesting retransmissionof those packets, from among those sent in MAP cycle N-1, which weresuccessfully received and successfully de-aggregated by the individualnode.

In some embodiments, if in a MAP cycle N−1, the second additional nodesent the individual node an aggregation frame including a plurality ofpackets only some of which were received by the individual node, theretransmission request sent by the individual node to the network accesscoordinator may request retransmission of less than all of the pluralityof packets and may include an indication, computed by the individualnode, of a slot duration to be used to retransmit the packets for whichretransmission is requested.

Some embodiments of the invention may include a method for transmittingpackets over a network of communication channels. The method may includecoordinating the access of a set of nodes to a synchronous network ofchannels interconnecting the set of nodes. The coordinating may includeproviding a plurality of slots in each MAP cycle for packet transmissionrequests sent to a coordinator by individual nodes in the set of nodes.In some embodiments, at least one individual node in the set of nodesmay be operative to utilize an individual slot from among the pluralityof slots to transmit to the coordinator both a reservation request and aretransmission request, the reservation request including a request totransmit a first packet to a first additional node and theretransmission request including a request that a second additional noderetransmit a second packet previously unsuccessfully transmitted fromthe second additional node to the individual node.

Some embodiments may include a method for transmitting packets over anetwork of communication channels. The method may include coordinatingthe access of a set of nodes, which may include at least first andsecond nodes, to a synchronous network of channels interconnecting theset of nodes. In some embodiments, if at least one individual packet hasbeen transmitted from the first node to the second node which did notreceive at least one packet, the second node may be operative to send aretransmission request to a network access coordinator requestingretransmission of at least one individual packet.

Typically, as a result of the de-aggregation process, the Rx node knowsthe size of a frame since size information is included in the frame'sheader. The Rx node may know some or all of the sizes of the individualpackets in the frame either because this information was included inpacket headers, and the packet headers were received even if theirassociated packets were not, or because the information regarding sizesof packets was included in the frame header. If a particular packet sizeis not known, the Rx node typically requests that all packets from thatpacket onward be re-transmitted. If all packet sizes are known, the Rxtypically requests re-transmission only of missing packets and easilyindicates a suitable slot duration as the sum of the known sizes of allmissing packets.

Positive or Negative Acknowledgements for properly received packets aretypically effected via the Reservation Request messages from thereceiving node to the network coordinator.

An acknowledgment message (“ACK”) is typically a single messagereferring to a burst of received packets. In the context of packetaggregation distinct negative acknowledgment messages (“NACKs”)typically correspond to individual packets in the aggregated receivedburst.

The network coordinator may include an Automatic Retransmission request(“ARQ”) mechanism. If so, it may be used as a proxy to convey one ormore ACK messages to the transmitting node and to retransmit one or moreimproperly received packets. The ARQ mechanism typically does notrequire additional bandwidth, in contrast to conventional retransmissionmechanisms.

Some embodiments of the invention may include a method forretransmitting a packet before initial transmission of a next-queuedpacket. Packet order is thus retained by not transmitting thenext-queued packet before receiving an acknowledgement of thealready-transmitted packet.

Table 1 lists abbreviations that are used in the description and FIGS.herein.

TABLE 1 Acronym Term RP Retransmission Protocol R-ACK ReceiptAcknowledgement RTR Retransmission Request RQ-T Retransmission RequestSignal RQ-S Retransmission Request Transmitter RQ-C RetransmissionRequest Coordinator ARQ Automatic Retransmission request MAP MediumAccess Plan ACK Acknowledgment Message NACK Negative AcknowledgmentMessage RR Retransmission Request P#Z Packet No. Z X→Y Information beingtransmitted from Node X to Node Y

FIG. 1 shows a timing diagram corresponding to one example of a MACaccess method for an illustrative coordinated network. A networkcoordinator controls access to network media by allocating transmissionopportunities to all network terminals. The coordinator thereby reducesor eliminates the likelihood that there will be contention in thenetwork. The coordinator may assign priorities to the transmission ofinformation based on information source, content, affect on QoS or anyother suitable criterion. Some coordinated networks have collision-freeperiods as well as collision periods. Others, such as those governed bythe MoCA Specification, have only collision free periods.

One prior art MAC Access Method is described in the MoCA MAC/PHYSPECIFICATION v1.0, Feb. 22, 2006. FIG. 1 shows the MoCA MAC schema forcoordination of network access by a network coordinator. The access timeis divided into MAP cycles which are managed by the network coordinator.Access rules for a MAP cycle may be defined in a MAP message sent in aprevious MAP cycle by the network coordinator to all nodes.

The FIG. 1 example includes three network nodes: coordinator, node 1 andnode 2. The coordinator sends transmission opportunities for MAP cycle Nin the MAP message of the MAP cycle N−1. Illustrative opportunities andsome corresponding illustrative precedents that may be associated withthe timing diagram of FIG. 1 are summarized in Table 2.

TABLE 2 Opportunity number Opportunity Precedent 1 Reservation request(“RR”) for node #1 2 RR for node #2 3 First data packet transmitted byBased on a MAP cycle node #1 to node #2 N − 1 node #1 request granted inthe MAP message of that cycle by the coordinator. 4 Second packettransmitted by node #1 to node #2 5 MAP message for cycle N + 1 Based onRR received (sent by coordinator) Opportunities Nos. 1 and 2. 6 Datatransmitted from node #2 to 7 Third data packet transmitted by node #1to node #2 8 Data transmitted from coordinator to node #1 9 Extensionpacket May be included if the data in opportunity 9 is less than aminimum burst size.

Typically, there is an Inter Frame Gap (IFG) between any two burststransmitted, and there is a minimum burst size. If data size is smallerthan the Min Burst Size an extension packet size may be allocated asshown in FIG. 1.

The IFG as well as the Min Burst Size typically cause additionaloverhead and reduce the effective data rate of the network, however,they contribute toward reliable operation of the modem.

Retransmission is useful for increasing the robustness of datatransfers, because a packet that was received with an error can beretransmitted. In particular, retransmissions are common in media thatare susceptible to impulse noises. Impulse noises are created by homeappliances as well as other noise sources and are received on wiredmedia such as phone lines and power lines. Other media, such as EthernetCATS wires and coaxial wires, are much less susceptible to impulsenoises due to their better isolation from external noises. An impulsenoise can be high enough in amplitude and long enough in time to causepacket errors or even packet loss.

If a coordinated network is to operate over noisy media (such astelephone lines or power lines) a Retransmission Protocol (“RP”) istypically employed to provide appropriate network performance. Thecoordinated network shown in FIG. 1 is designed to operate over “quiet”media. An example of a network designed to provide a robust and reliablehome networking over coaxial cables is that described the MoCASpecification. Embodiments of the invention may include providing an RPin connection with a coordinated network protocol, such as that setforth in the MoCA Specification. The methods described herein may beused efficiently in conjunction with the MoCA Specification in othersuitable media, such as power lines and phone lines.

In some embodiments of the invention, the network coordinator may selectfrom several retransmission protocols. One protocol may be set as adefault method that is implemented by all nodes. A general algorithm foran RP is as follows:

-   1. The transmitting node transmits a packet or several packets and    waits for an acknowledgement;-   2. A. If the receiving node receives the packet correctly, the    receiving node sends a Receive Acknowledgement (R-ACK).

B. If the receiving node does not receive the packet correctly, thereceiving node sends a Retransmission Request (RTR).

-   3. The transmitting node, upon receiving an R-ACK or RTR,    retransmits the packet.-   4. The transmitting node retransmits the package if neither an R-ACK    nor RTR were sent.

The maximum number of retransmissions is typically a parameter of a datastream. The stream may include video data. The stream may include voicedata. The stream may include browsing data. The stream may include anysuitable type of data. After the transmitting node has sent the maximumnumber of retransmissions, no further attempts to transmit the packetare made. The receiving node typically forwards the received packets inthe order of transmission by the transmitting node. If a packet ismissing, the receiver node typically does not forward the next packetuntil the missing packet is received unless the maximum number ofretransmissions has been reached.

Five illustrative ARQ protocol-based methods, and three more generalretransmission methods based thereupon, are now described. In someembodiments of the invention, nodes may select an ARQ protocol duringthe establishment of a connection. One of the options is typically setas a default method that is implemented by all nodes. For example,Method #1 can be the default method. In general, ARQ protocols follow analgorithm such as:

-   1. The transmitting node sends a reservation request (“RR”)    corresponding to an expected transmission of a packet. If ARQ is    employed, the node so signifies in the RR.-   2. The transmitting node transmits the packet and waits for an ACK.-   3. The receiving node receives the packet and checks if it has been    received correctly.-   4. If the packet has been received correctly the receiving network    sends an ACK.-   5. If the packet has been received incorrectly, or not at all, the    receiving node either sends a NACK or does not reply.-   6. Upon receiving an ACK or a NACK, the transmitting node decides    whether to retransmit the packet or not. If neither ACK nor NACK    were received the transmitted node may retransmit the packet.-   7. The number of retransmissions is a parameter of the connection.

FIG. 2 shows illustrative method 1 (Immediate ARQ), which may includesome or all of the following steps in a suitable order:

-   1. The transmitting (TX) node in its reservation request (RR)    requests to transmit a packet to the receiving node indicating that    transmission is under ARQ.-   2. The coordinator allocates two time slots for the transmission of    this packet. The first slot is for transmission of the packet by the    TX node. The second slot is for transmission of the ACK/NACK message    by the receiving (RX) node immediately following the TX. In some    embodiments, the coordinator allocates slots that are equal to a    minimum burst size.-   3. The TX node sends the packet after the TX node receives a grant    message indicating that coordinator granted a RR for the packet.-   4. The RX node sends the ACK/NACK in the second slot.-   5. The TX analyzes the ACK/NACK message and, if NACK is received, in    the next RR opportunity the TX node request for retransmission the    packet.-   6. The coordinator receives the RR and grants the request if the    maximum number of retransmission requests has not yet been reached.-   7. If granted, the TX node retransmits the packet in the next MAP    cycle.-   8. This procedure can repeat itself several times according to the    parameters of the ARQ of this connection.

FIG. 3 shows illustrative method 2 (Single Frame ARQ), which may besimilar to method 1 (shown in FIG. 2), except that the allocation forthe ACK/NACK message does not necessarily immediately follow the TX nodetransmission.

FIG. 4 shows illustrative method 3 (Multiple Frame ARQ), which may besimilar to method 2, except that one ACK/NACK is sent to acknowledge inaggregate more than one received packet. For example, FIG. 4 shows anACK for packet 2 and a NACK for packet 3.

FIG. 5 shows illustrative method 4 (ACK/NACK Embedded in RR—included inARQ messages) enables more efficient ARQ throughput. The ACK/NACKmessage is not transmitted on its own and instead is embedded in the RRmessage of the RX node in MAP cycle N+1. When RR messages are shorterthan the Min Burst Size time, additional overhead for the ACK/NACK maybe conserved (although higher latency may be involved).

FIG. 6 shows illustrative method 5 (Very short Immediate ACK/NACK),which may be similar to Method 1, except that the ACKINACK is a veryshort message, such as a 64 bit BPSK series that is detected by the PRY.This is efficient with respect to throughput, but may require changes tothe PRY and fast response to detection of error (or no error) bytransmission of the short ACK/NACK.

FIG. 7 shows illustrative method 6 (Retransmission Request Transmitter(RQ-T)), which may be operative to send single or burst R-ACK/RTRmessage to the transmitter. In some embodiments of the invention, themethod may include some or all of the following steps in a suitableorder such as the following:

-   1. The transmitting (TX) node in its reservation request (RR)    requests to transmit one or multiple frames to the receiving node.-   2. The transmitting node indicates in the RR the following    information:

A. An indication that the frame is in Retransmission Protocol;

B. An indication that the method of RP is preferred over RQ-T; and

C. Single or burst RQ-T.

-   3. The coordinator allocates slots for the transmission and RP of    the frames typically in one of the following orders:

A. If single RQ-T is used, a slot is allocated for transmission of thefirst frame by the TX node, a slot is then allocated for transmission ofthe single RQ-T message by the RX node, and finally, slots are allocatedfor the rest of the frames deemed “required” by the TX node.

B. If a burst of RQ-T is used, slots are allocated for transmission ofall frames deemed “required” by the TX node, and one slot is thenallocated for transmission of the burst RQ-T message by the RX node.

-   3.1 In some embodiments, the coordinator may be operative to    allocate one or more slots for an RQ-T message immediately after a    packet or packets that required RQ-T or in a corresponding or    subsequent MAP.-   4. The coordinator indicates to the RX node which frames are to be    acknowledged in each RQ-T message.-   5. The TX node sends the frames according to the grant received from    the coordinator.-   6. The RX node sends an RQ-T message in the RQ-T slots granted by    the coordinator.-   7. The RQ-T message is sent, with an indication of R-ACK or RTR, for    frames that requested acknowledgment in that specific RQ-T message.-   8. The TX node analyzes the RQ-T message and may, if    application-appropriate, add an RR element in the next RR    transmission for retransmission of the frames missed by the RX node.-   9. The coordinator receives the RR and may grant the slot according    to the above steps.-   10. The foregoing actions may be repeated several times, provided    that the maximum number of retransmissions is not exceeded.

FIG. 8 shows illustrative method 7 (Retransmission Request Signal(RQ-S)), which may be operative to send single R-ACK1RTR signal to thetransmitter. In some embodiments, the RQ-S may include a short signalwith an indication of R-ACK or RTR which may be allocated immediatelyfollowing each burst requiring retransmission under the RQ-S method.Method 7 typically comprises some or all of the following steps in asuitable order such as the following:

-   1. The transmitting (TX) node in its reservation request (RR)    requests to transmit one or multiple of frames to the receiving    node.-   2. The transmitting node indicates in the RR the following    information:    -   A. An indication that the frame is in Retransmission Protocol;        and    -   B. An indication that the RP method is preferred over the RQ-S        method.-   3. The coordinator allocates, for each burst with RQ-S, the slot for    transmission of the frame by the TX node and the slot for    transmission of the RQ-S signal by the RX node.-   4. The coordinator and the RX node check whether the RQ-S signal    bears an indication of R-ACK or RTR.-   5. If the RQ-S indicates R-ACK, the TX node clears the packet.-   6. If the RQ-S indicates RTR, the coordinator allocates a slot for    retransmission of the frame by the TX node.-   7. If the coordinator has not received the RQ-S and the TX node    receives it with R-ACK, the coordinator allocates a slot for    retransmission and the TX node sends an empty frame.-   8. If the TX node has not received the RQ-S and the coordinator    receives it with an R-ACK indication, the coordinator indicates that    the frame was received correctly in the next allocation slot of the    flow.-   9. The R-ACK or RTR indication is on the whole frame with no    indication per packet if the frame is aggregate.

A short RQ-S signal is easy to distinguish from other network signals. Ashort RQ-S may use a commonly known (MoCA, e.g.) PHY preamble used bythe network with different parameters. For example, an RQ-S with R-ACKindication may comprise 8 S signals followed by 4 L2 series followed byan inverted 4 L2 series followed by an S quiet period and two L1sequences. An RQ-S with RTR indication may comprise 8 S signals followedby 4 L2 series followed by inverted 4 L2 series followed by an S quietperiod and two L4 sequences, such as that shown below.

 S = {0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1,0, 0, 1, 1, 1, 1, 1, 0} L4 = {1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0,1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1,0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0,0, 1} L2 = {1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 0,0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1,1, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 1, 1, 0, 1} L1 = {0, 0,0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0,1, 1, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 1, 1,1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0}

FIG. 9 shows illustrative method 8 (Retransmission Request Coordinator(RQ-C)), which may be operative to send burst R-ACK or RTR to thenetwork coordinator. In some embodiments, the acknowledgement indicationis typically sent to the coordinator in the Reservation Request Message.The method typically comprises some or all of the following steps in asuitable order such as the following:

-   1. The transmitting (TX) node in its reservation request (RR)    requests to transmit one or multiple frames to the receiving node.-   2. The transmitting node indicates in the RR the following    information:

A. That the frame is in Retransmission Protocol; and

B. That the method of RP is preferred over RQ-C.

-   3. The coordinator allocates slots for transmission of the frames by    the TX node.-   4. In the next MAP cycle the coordinator allocates an RR slot for    the RX node (even if the RX node does not need an RR slot for its TX    frames).-   5. The RX node checks which frame s were received correctly and    which were not, from all TX nodes sent to it in the previous MAP    cycle.-   6. The RX node sends, in the RR message, an R-ACK or RTR indication    for all frames which employ RQ-C.-   7. The RTR is typically sent with some or all of the following    information:

A. The sequence of frame s for retransmission;

B. If the frame was an aggregation frame and a portion of its packetswas received incorrectly, send the packet sequence of the missedpackets;

C. The durations used for retransmission of these frames. If the wholeframe is to be retransmitted, the duration may be taken from the RX dataslot, whereas if only a portion of the frame is to be retransmitted, theduration may be computed according to the PRY profile of the TX and RXnodes.

-   8. In the next MAP cycle, the coordinator allocates slots to be used    by the RX node for retransmission of the frames by the TX node.-   9. If the R-ACK for some frames is sent in the RR message, the    coordinator indicates in the next MAP that these frames were    received correctly.-   10. The TX node receives a MAP with slots for retransmission of the    lost frames/packets and with an indication of which frames/packets    were received correctly by the RX node.-   11. The TX node clears frames/packets received correctly and    retransmits lost frames/packet.-   12. The RX node may re-send RTR for a specific frame/packet until a    limit on the number of retransmissions is reached.-   13. if the limit is reached, the frame/packet may still not have    been received.

Methods 6 or 8 may be usable for high bit rate stream such as RD video.

Method 7 may be usable for low bit rate stream such as voice in whichthe RX node is only a listener. This method may reduce bandwidth whenthe RR is allocated infrequently or not at all for the TX or RX nodes.The RR is not allocated to the TX node when the stream is sent in anunsolicited manner.

Method 8 may save bandwidth for RP by merging the RP in the RR slots. Tothe extent that the RX node receives streams in RP, the saved timeincreases.

FIG. 10 shows a single or multi-chip module 1002 according to theinvention, which can be one or more integrated circuits, in anillustrative data processing system 1000 according to the invention.Data processing system 1000 may include one or more of the followingcomponents: I/O circuitry 1004, peripheral devices 1006, processor 1008and memory 1010. These components may be coupled together by a systembus or other interconnections 1012 and are disposed on a circuit board1020 in an end-user system 1030 that may be in communication with a coaxmedium transmitting packets in accordance with the systems and methodsdiscussed above.

FIG. 11 is a simplified block diagram illustration of a home networksystem 1102 that uses a coax backbone 1105. The home network system 1102of FIG. 11 is operative for transmitting packets over coax backbone 1105within a home 1100. The home network system 1102 includes first node1110, second node 1120 and network access coordinator 1115. First node1110, second node 1120 and network access coordinator 1115 areconfigured to communicate over coax backbone 1105.

It is appreciated that for clarity the description throughout thespecification, including specific examples of parameter values providedherein, is sometimes specific to certain protocols such as the MoCAand/or Ethernet protocols however, this is not intended to be limitingand the invention may be suitably generalized to other cable protocolsand/or other packet protocols. For example, use of terms, such as Map,Allocation Unit, Reservation Request etc. which may be specific to aparticular protocol such as MoCA or Ethernet, to describe a particularfeature or embodiment is not intended to limit the scope of that featureor embodiment to that protocol specifically; instead the terms are usedgenerally and are each intended to include parallel and similar termsdefined under other protocols.

It is appreciated that software components of the present inventionincluding programs and data may, if desired, be implemented in ROM (readonly memory) form including CD-ROMs, EPROMs and EEPROMs, or may bestored in any other suitable computer-readable medium such as but notlimited to disks of various kinds, cards of various kinds and RAMs.Components described herein as software may, alternatively, beimplemented wholly or partly in hardware, if desired, using conventionaltechniques.

Features of the present invention which are described in the context ofseparate embodiments may also be provided in combination in a singleembodiment. Conversely, features of the invention which are describedfor brevity in the context of a single embodiment may be providedseparately or in any suitable subcombination.

What is claimed is:
 1. A system for communication, the systemcomprising: a network access coordinator configured to communicate witha first node and a second node via a network backbone, wherein thenetwork access coordinator is configured to coordinate access of thefirst node and the second node to the network backbone, wherein thenetwork access coordinator is configured to receive, from the first nodein a first time period, a first reservation request to transmit a firstpacket to the second node, wherein the network access coordinator isconfigured to allocate, in response to the first reservation request, afirst slot in a second time period for the first node to transmit thefirst packet to the second node, wherein the network access coordinatoris configured to receive a first reply from the second node and conveythe first reply to the first node, the first reply comprising anindicator of whether the second node received the first packet, andwherein the network access coordinator is configured to receive, fromthe first node in a third time period, a second reservation request toretransmit the first packet to the second node based at least on adetermination that the second node did not receive the first packet. 2.The system of claim 1, wherein the network backbone comprises at leastone of a phone line, a power line, or a coaxial line.
 3. The system ofclaim 1, wherein the network backbone is located within a home.
 4. Thesystem of claim 1, wherein the network access coordinator is locatedwithin a home.
 5. The system of claim 1, wherein the network accesscoordinator is configured to allocate a second slot in a fourth timeperiod for the first node to retransmit the first packet to the secondnode when a maximum number of retransmissions has not yet been reached.6. The system of claim 5, wherein the first time period, the second timeperiod, the third time period, and the fourth time period are mediaaccess plan (MAP) cycles.
 7. The system of claim 5, wherein the firsttime period, the second time period, the third time period, and thefourth time period are consecutive MAP cycles.
 8. The system of claim 5,wherein the second slot is not immediately after the first slot.
 9. Thesystem of claim 1, further comprising the first node and the secondnode, wherein the first node is configured to transmit a second packetto the second node, and wherein the first reply further comprises anindicator of whether the second node received the second packet.
 10. Thesystem of claim 9, wherein the first node is configured to transmit thesecond packet to the second node in the second time period that, isafter the first time period.
 11. The system of claim 1, wherein thenetwork access coordinator is configured to receive, from the secondnode, a second reservation request, and wherein the second reservationrequest comprises the first reply.
 12. The system of claim 1, whereinthe first time period, the second time period, and the third time periodare consecutive MAP cycles.
 13. The system of claim 1, wherein the firstreply comprises a binary phase-shift keying (BPSK) message.
 14. Thesystem of claim 13, wherein the BPSK message is 64 bits.
 15. A methodfor coordinating access of a first node and a second node to a networkbackbone, the method comprising: receiving, by a network accesscoordinator from the first node in a first time period, a firstreservation request to transmit a first packet to the second node;allocating, by the network access coordinator in response to the firstreservation request, a first slot in a second time period for the firstnode to transmit the first packet to the second node; receiving, by thenetwork access coordinator from the second node, a first reply, thefirst reply comprising an indicator of whether the second node receivedthe first packet; conveying, by the network access coordinator, thefirst reply to the first node; and receiving, by the network accesscoordinator from the first node in a third time period, a secondreservation request to retransmit the first packet to the second node,the second reservation request being based at least on a determinationthat the second node did not receive the first packet.
 16. The method ofclaim 15, wherein the network access coordinator is located within ahome, and wherein the network backbone comprises at least one of a phoneline, a power line, or a coaxial line, and wherein the first time periodand the second time period are media access plan (MAP) cycles.
 17. Themethod of claim 15, further comprising receiving a request to retransmitthe first packet.
 18. The method of claim 15, wherein the first replycomprises a reservation request message.
 19. A non-transitorymachine-readable medium encoded with executable instructions for amethod of coordinating access of a first node and a second node to anetwork backbone located within a home, the method comprising:receiving, by a network access coordinator from the first node in afirst media access plan (MAP) cycle, a first reservation request totransmit a first packet to the second node, wherein the network accesscoordinator is located within the home; allocating, by the networkaccess coordinator in response to the first reservation request, a firstslot in a second MAP cycle after the first MAP cycle for the first nodeto transmit the first packet to the second node; receiving, by thenetwork access coordinator from the second node, a first reply, thefirst reply comprising an indicator of whether the second node receivedthe first packet; conveying, by the network access coordinator, thefirst reply to the first node; and receiving, by the network accesscoordinator from the first node in a third MAP cycle, a secondreservation request to retransmit the first packet to the second node,the second reservation request being based at least on a determinationby the first node that the second node did not receive the first packet.20. The non-transitory machine-readable medium of claim 19, wherein thefirst reply comprises a reservation request message.